# Bookstore — Part 11 ch.03 "API Priority & Fairness": bound the BookstoreTenant
# operator's apiserver traffic into its OWN PriorityLevel + FlowSchema so a
# buggy reconcile (a hot-loop LIST/WATCH/UPDATE storm) cannot starve the
# control plane for everyone else. This is the noisy-neighbor protection the
# chapter builds.
#
# !!! NOT CRD-BACKED — FlowSchema and PriorityLevelConfiguration are BUILT-IN
# (flowcontrol.apiserver.k8s.io/v1, GA since v1.29). So unlike the CRD/webhook
# files this one dry-runs/applies CLEAN on any v1.30+ cluster with no operator,
# no CRD, nothing installed:
#   kubectl apply --dry-run=client -f config/apf/bookstore-operator-apf.yaml
#   flowschema.../...  created (dry run)
#   prioritylevelconfiguration.../... created (dry run)
# (No CRD-intrinsic caveat — stated explicitly, the inverse of the CRD files.)
#
# Model: a request is matched by the HIGHEST-precedence FlowSchema whose rules
# fit (subject + verb + resource); that names a PriorityLevelConfiguration,
# which gives the request a concurrency share and a fair queue. A Limited level
# that floods only drains ITS OWN queue — other levels (and the built-in
# system / leader-election / workload-* levels) are unaffected.
apiVersion: flowcontrol.apiserver.k8s.io/v1
kind: PriorityLevelConfiguration
metadata:
  name: bookstore-operator
spec:
  type: Limited # bounded (NOT Exempt — Exempt = unthrottled, for system only)
  limited:
    # Share of the apiserver's total concurrency this level may use. Low on
    # purpose: a teaching operator should never be able to crowd out workload
    # controllers. Concurrency is shared proportionally to all levels' shares.
    nominalConcurrencyShares: 10
    # May lend up to half its unused concurrency to other levels when idle...
    lendablePercent: 50
    # ...and borrow up to 20% on top of its nominal share when others are idle.
    borrowingLimitPercent: 20
    limitResponse:
      type: Queue # queue excess requests rather than 429 immediately
      queuing:
        queues: 16
        handSize: 4 # shuffle-sharding: isolates a bad flow from good ones
        queueLengthLimit: 25 # beyond this, requests get 429 (Too Many Requests)
---
apiVersion: flowcontrol.apiserver.k8s.io/v1
kind: FlowSchema
metadata:
  name: bookstore-operator
spec:
  # Lower number = higher precedence. The default catch-all is 9000 and
  # workload-leader-election is ~200; 500 places the operator's traffic into
  # its bounded level BEFORE it falls through to the global catch-all (where a
  # busy operator WOULD compete with every other unclassified client).
  matchingPrecedence: 500
  priorityLevelConfiguration:
    name: bookstore-operator
  distinguisherMethod:
    # Fan out fairness per-namespace so one tenant namespace's churn does not
    # starve another within the operator's own level.
    type: ByNamespace
  rules:
    - subjects:
        - kind: ServiceAccount
          serviceAccount:
            name: bookstore-operator-controller-manager
            namespace: bookstore-operator-system
      resourceRules:
        - verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
          apiGroups: ["bookstore.example.com", "", "apps"]
          resources: ["bookstoretenants", "bookstoretenants/status", "namespaces", "configmaps", "services", "deployments"]
          namespaces: ["*"]